Various polymers are produced by procedures in which a solution of the desired polymer has to be separated into the polymer and the solvent. Particularly, for synthetic rubber production, this solvent removal constitutes a major problem. For high quality polymers frequently high purity solvents are used. The quantity of such solvents lies normally in the range of 3-10 parts by weight of solvent or diluent per 1 part by weight of polymer. Essentially complete recovery of the solvent constitutes an important economic consideration.
It is known in the art that the solvent or diluent of a polymer solution can be and preferably is removed by evaporating this solvent. It is also known that a devolatilizing extruder can be used for this purpose. The extruder utilizes, at least partly, mechanically introduced energy to evaporate the solvent. The cost of such an energy input becomes quite high and large capital investments are necessary for installing these devolatilizing extruders.
A general problem in connection with devolatilizing extruders resides in the throughput. The capacity of, e.g., rubber plants is frequently limited by the devolatilizing extruders which constitute a bottleneck in the production. An increased throughput through these extruders would increase the overall capacity of the plant without the necessity of adding further equipment and thus essentially without further capital expenditure. Furthermore, a serious technical problem occurs in connection with devolatilizing extruders. For reasons that are not quite understood, a fairly severe surging of the power input to the motor driving the extruder occurs. To increase throughput and solvent removal rate and to reduce the power surging of a devolatilizing extruder are two of the main problems that are solved by the present invention.